For the past few years, “American Idol” has had to contend with an ever-changing roster of judges, competition from NBC’s “The Voice” and ratings declines. Add one more destabilizing challenge to the pile: hungry zombies on cable.

Advertisers are willing to pay more for a package of ads to accompany a fresh episode of AMC’s “The Walking Dead” than they are for a single 30-second spot on “Idol,” the Fox competition program that has dominated primetime for years. That groundbreaking move for cable revealed in a comprehensive Variety survey of ad prices of primetime TV programs for the 2013-14 television season.

“Dead” is, arguably, the priciest scripted program on TV, but simply put, there is no one single price for a TV commercial. TV networks typically sell schedules of advertising in the form of a package of ads spread out across the week and many different programs, not specific spots in certain shows (the most notable exception: the Super Bowl). Still, “Dead’s” ascent is a milestone for the cable biz and undoubtedly cause for some jitters among broadcast TV execs.

The Variety survey was compiled using as many as six estimates provided by top ad-buying firms, along with information from other media sources. The figures are averages and are meant to be taken as directional indicators of advertising cost.

Nonetheless, the numbers do provide an interesting look at which dramas, comedies and reality series attract the most clamor from paying customers. For instance, advertisers are willing to pay an average of $326,000 for a strip of ads that run Sunday nights when AMC airs a new episode of “Walking Dead” several times in one evening. CBS’ “The Big Bang Theory,” which commands an average of $317,160 for a 30-second spot, is the most expensive broadcast-network program for advertisers.

Still, predictably, ads are more expensive for two long-running and highly watched sports programs. NBC’s “Sunday Night Football” is the costliest program of the season for sponsors, with advertisers paying an average of $628,000 for a 30-second spot, followed by ESPN’s “Monday Night Football,” which commands an average of $408,000 for a 30-second commercial, according to Variety’s survey.

“American Idol” has long been the costliest non-sports show on TV for sponsors. Indeed, for several years, even “Sunday Night Football” took a back seat to the music competition series. Over the past two years, however, the maturing competition series has seen ratings tumble, and with them its ad prices – so much so that sponsors are paying more for appearances in “Walking Dead,” as well as CBS’ “Big Bang Theory,” than they are for “Idol’s” Wednesday-night edition. And the prices advertisers pay for “Idol” on Thursdays are on average less than what they fork over for both editions of NBC’s “The Voice,” and even Fox’s Kevin Bacon starrer “The Following.”

Last season, advertisers paid an average of $340,825 for a 30-second spot on the Wednesday-night airing of “Idol,” and an average of $296,002 for the show’s Thursday-night run. This season, those rates have declined to $281,600 on Wednesday and $257,926 on Thursday, according to the Variety survey. To be sure, the show’s prices may go higher: One estimate puts some ads for “Idol” at more than $300,000, and the cost of sponsoring the show is known to rise as the finalists square off in May.

Other programs have seen their prices increase, particularly as they generate better ratings among the key adults 18-49 demographic. Last season, a package of “Walking Dead” commercials was going for between $200,000 and $260,000 during the upfront, according to ad buyers, compared with an average of $326,000 this fall. A 30-second ad in “Big Bang Theory” last season brought in an average of $275,573 last season, valuing this year’s increase at more than $35,000 per spot.

“Sunday Night Football” has also seen its prices rise, owing to the scarcity of live programming that attracts massive crowds. It has climbed by more than $80,000 per 30-second spot from last season’s $545,142.

Others among the 10 most expensive programs for advertisers include: the Tuesday-night airing of “The Voice” on NBC, which commands an average of $273,714 for a 30-second spot, compared with $225,337 last season; Fox’s “The Following,” an average of $264,300 for a 30-second spot, compared with $194,425 last season; the Monday-night airing of “The Voice” on NBC ($259,240 vs. $239,866 last season); and ABC’s “Modern Family,” which fell to $249,025 from $330,908 last season.

Gone from the ranks of the top 10 after many years are Fox’s “The Simpsons” and “Family Guy” and CBS’ “Two and a Half Men,” along with newer additions including Fox’s “New Girl” and CBS’ “2 Broke Girls.” Without the cable entries, however, “Simpsons” and “New Girl” would have made the cut.

Not all of the priciest shows for advertisers air in primetime. The cost of a 30-second spot in Fox’s NFL Sunday afternoon broadcasts is said to reach into the $600,000 range, while a spot in its post-game coverage, known as “The OT,” can cost more than $400,000.

The most expensive new programs for advertisers this season depend on a single factor: location. The three priciest programs all follow shows known to bring in broad audiences. On CBS, “The Millers,” which directly follows “Big Bang Theory,” commands an average of $176,777 for a 30-second spot. On NBC, “The Blacklist,” which follows “The Voice” on Monday nights, commands an average of $174,493. Even “The Crazy Ones,” the Robin Williams-starrer that follows “The Millers,” benefits from the lead-in show; advertisers are paying an average of $173,727 for a 30-second spot on the show – about a copywriter at an ad agency.